From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CD001C0044C for ; Mon, 5 Nov 2018 18:22:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7F9592086C for ; Mon, 5 Nov 2018 18:22:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=android.com header.i=@android.com header.b="LZ3rc6SX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F9592086C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=android.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387876AbeKFDmy (ORCPT ); Mon, 5 Nov 2018 22:42:54 -0500 Received: from mail-pl1-f195.google.com ([209.85.214.195]:40443 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387705AbeKFDmy (ORCPT ); Mon, 5 Nov 2018 22:42:54 -0500 Received: by mail-pl1-f195.google.com with SMTP id q19-v6so1854845pll.7 for ; Mon, 05 Nov 2018 10:22:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=android.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=gxSwJRH2SI+YwdfjFaCuvhRWPV8qtgADoq2dL0nBJS8=; b=LZ3rc6SX/md2r6z95NjLyd4MUNp6BdSu7L9ty8xlj1jUI+aJExwFjqW9qdjOMohg3r z5LDg4u0dImnGuMVhbnT16tO/SJ4TtuUW98fTGvDTq4Gq7z74T+vdO0dW8u5l+UfgoEL HMH9Sx13YqSAEsL6H2tvCSMYo6XWVxLw2o7z3wY2Bu1M2UF2sOejJ0f26+t2icUs1qby WZaQKVYyb3IlX/yuBEsih2DenRRyJHjWVnPXfkisQTlyJTjp/uFlVam8m+AqmxDmTGxJ ObhWIzv0kesFe88x+1K74B5lFL01xygoUsxpg/q7jaLtHuwBLt9RmpYfuLTXEsVT1fQq 2jMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=gxSwJRH2SI+YwdfjFaCuvhRWPV8qtgADoq2dL0nBJS8=; b=RTwpuIOd6sm/ijCdjppB5KDlom+SSzCTMSuIoeZYxX2F86EuTqvahuIbEWmIjKfQbj BpBY723C6XMZdtLzY/ek3n+jPCqcoLKd0x4k26JjFRE7lTQUtbcmBzFfvgmbc02SB1AW eGqtr8e4OiCBJGDG0BNLQl+tCoOgZrkaM3kqwD0z7fizLK2cSsorO0MVNx5Kj89WGGZH oNZ3YLhnURC5sf65x6M0q0a8u/rPIuGFmrNbB+iXNLcNK2IdQufHoNGccO7HuGnCxwQp YxCGpJu5njRy/+BzE3PFlUb7Zjyriaagn5q5JxBT8zE+YajtyNqHTZHP+665kYWRYRQZ zi7Q== X-Gm-Message-State: AGRZ1gI+ZGCxQSgeJ1e3MYaGxzG6RVAd1N0fas/NABZZcX4z+HZcQurH aBVUL9nojyNGz8x/gneLBizQ/mRk14g= X-Google-Smtp-Source: AJdET5dkEhuW+mGbHtkHFWvfEc1+zCjNrgGRI7bND2V5aXXLfbRpi8OyFzQitdZRSabllwSSzL935Q== X-Received: by 2002:a17:902:bd8d:: with SMTP id q13-v6mr23172144pls.167.1541442119689; Mon, 05 Nov 2018 10:21:59 -0800 (PST) Received: from nebulus.mtv.corp.google.com ([2620:0:1000:1612:b4fb:6752:f21f:3502]) by smtp.gmail.com with ESMTPSA id s184-v6sm53788626pfb.46.2018.11.05.10.21.58 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 05 Nov 2018 10:21:58 -0800 (PST) From: Mark Salyzyn To: linux-kernel@vger.kernel.org Cc: Mark Salyzyn , Miklos Szeredi , Jonathan Corbet , Vivek Goyal , "Eric W . Biederman" , Amir Goldstein , Randy Dunlap , Stephen Smalley , linux-unionfs@vger.kernel.org, linux-doc@vger.kernel.org Subject: [PATCH v6 0/2] Date: Mon, 5 Nov 2018 10:21:40 -0800 Message-Id: <20181105182146.233025-1-salyzyn@android.com> X-Mailer: git-send-email 2.19.1.930.g4563a0d9d0-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh Assumption never checked, should fail if the mounter creds are not sufficient. overlayfs: override_creds=off option bypass creator_cred By default, all access to the upper, lower and work directories is the recorded mounter's MAC and DAC credentials. The incoming accesses are checked against the caller's credentials. If the principles of least privilege are applied, the mounter's credentials might not overlap the credentials of the caller's when accessing the overlayfs filesystem. For example, a file that a lower DAC privileged caller can execute, is MAC denied to the generally higher DAC privileged mounter, to prevent an attack vector. We add the option to turn off override_creds in the mount options; all subsequent operations after mount on the filesystem will be only the caller's credentials. The module boolean parameter and mount option override_creds is also added as a presence check for this "feature", existence of /sys/module/overlay/parameters/overlay_creds Signed-off-by: Mark Salyzyn Cc: Miklos Szeredi Cc: Jonathan Corbet Cc: Vivek Goyal Cc: Eric W. Biederman Cc: Amir Goldstein Cc: Randy Dunlap Cc: Stephen Smalley Cc: linux-unionfs@vger.kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org v2: - Forward port changed attr to stat, resulting in a build error. - altered commit message. v3: - Change name from caller_credentials / creator_credentials to the boolean override_creds. - Changed from creator to mounter credentials. - Updated and fortified the documentation. - Added CONFIG_OVERLAY_FS_OVERRIDE_CREDS v4: - spelling and grammar errors in text v5: - beefed up the caveats in the Documentation - Is dependent on "overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh" "overlayfs: check CAP_MKNOD before issuing vfs_whiteout" - Added prwarn when override_creds=off v6: - Drop CONFIG_OVERLAY_FS_OVERRIDE_CREDS. - Do better with the documentation, drop rationalizations. - pr_warn message adjusted to report consequences.